Resilient bushing and method and apparatus for making same



o. B. WELKER 2,110,783

RESILIENT BUSHING AND .METHOD AND APPARATUS FOR MAKING SAME'V FiledApril 25, 1956 2 sheets-sheet 1 INV ENT OR.

ORNEYS March 8, 193s.

INVENTOR, BY QSC-AR .5 WEL/ER `v M l 2 Sheets-Sheet 2 o. B. WELKERlvFiled April 25, 19:56

94 Zim RESILIENT BUSHING AND METHOD AND APPARATUS OR MAKING SAME March8, 1938.

ATToRNEY atented Mar. d, i938 j "'UNi-TED STATES' .anim

PATENT oFrlc autres RESILIENT BUSHING AND METHOD APPARATUS FOR MAKINGSAME Oscar B. Welker, Middletown, Genn., assgnor to Albert R. Teare,Cleveland, Ohio, trustee Application April 25, llliii,l Serial No.76,392

l Claims. (Cl. 2li-83.2)

characteristics, which enhance the quality of the finished product, andwhich' extend ,its.avai1.

ability for use.

Many forms of elastic connections, or bushings of the type referred tohave been placed upon the market, but experience has shown that therearecertain objections inherent in them. AFor example, in one form, thehollow rubber tube or I sleeve has been assembled by rst compressing itby inserting it into the outer tube and then further compressing it bythe use ofvan expanded mandrel before the inner tube is inserted intoplace. The resulting bearing is thereby limited in length and thestressesare distributed lunequally from one end to the other.

l Another form of bearing 'has been made by curing the rubberbetweenconcntric tubes. Thev shrinkage of the rpbber during the coolingoperation is then depended upon to place it under tension.A As a result,the rubber is unable to withstand very much repeated torsional vmovementunder load. Moreover, the rubber,.being under tension, defiects more-than under compression, thereby allowing the `inner tube to move morereadily out of center under dead load.A

` In making a bearing of this type, it is important that the rubber beplaced under a high degree of compression and that the stresses bedistributed uniformly throughout the rubber, for uniform distributionresults in greater Vfrictional resistance and a longer 'life cf therubber.

An eort to accomplish this resulthas'included a method "of manufacturein which-the rubber sleeve has been slipped onto an inner tube fornearly its entire' length and then compressed by pressing the outer tubeinto place. This method, however, did not place the rubber under asufil- -cient `degree of compression to make a practical joint, anddid-.not permit a bearing to be made in unlimited lengths.- Moreoven itdid not distribute facture, the rubber is not uniformly compressed y forthe greatest stress is at the endswhere the attaching force is applied.y v.

A further eilortto overcome the dimculties y length of the material.

- enumerated has included )the curing ot a mass of rubber to the innermember and then forcing the assembly endwise into an outer member.`Under such practice however, the` rubber can not flow on the bondedarea and hence the flow Vv,takes 5 place only in the unbonded area, andhence the stresses are unequally distributed. A further objectionto thecuring operation is the fact that it is too expensive to be practicaland that the length of bushing produced is limited to very` An object ofmy invention is to make a resilient bearingin which the intermediatelayer of Aelastic material i`s so stretched at the time of its assem?bly between the inner and outer tubes, that the stresses are equallydistributed throughout thev The invention also. includes a method ofmanufacturel by means of which resilientbearings may be made in anyvdesiredlength thereby extending the field of usjefulness of suchbearings to an extent hitherto unknown. An additional) object is to makethe bearings in multiple, regardless of the shape of the outer member.

`Referring now to the drawings, Fig. 1 is a top 25 plan View ci amachine for maklngthe torsional bushings in accordance with myinvention; Fig. 2 is a vertical section taken-on the lineZ--Z in Fig. land shown on'a scale larger than that otFig. 1; Fig. 3 is an end view ofthe ltorsional bushing; Fig. 30 4 Ais a section taken on the linev d-iiin Fig. 3; Fig. 5 is a sectionshowing a modified form of construction ofthe stock from which the elastic 'sleeves are' made; Fig. 6 is a sideelevation partly in section, of the rubber stock; Fig. 7 is a side 35elevation of the `machine; Figsf, 9 and l0 are sections taken on thecorrespondingly numbered lines in Fig. 1; and Fig. ll is a sideelevation of an assembled unit before the sections have been cuttherefrom.

In Figs. 3 and d, the bushing, which is made inl accordance with mylinvention, comprises anini ner member it, an outer member i i and anintermediate member l2, all of which are shown as d being cylindrical inshape and as having a commonaxis. The inner and outer members arepreferably made of metal, While the intermediate member is made ofelastic material, such as rubber. The present invention is not onlyconcerned f with the method of inserting the eiastic sleeve in a placebetween the 'outer and inner members 'but is also Iintended to includethe article that is made thereby. as well Aas the apparatus for pro=ducing it. y M

The preferred manner oi carrying out my inf.

. -be quickly inserted within the machine.

vention comprises the formation of rubber stock into a long tube, thebody of which is indicated at i5. One end of the tube is closed and theopposite end is open. The closed end in one form of the invention may beformed by a plug I6, the

-outer end of which is reduced and is closely embraced by the stock. Aring I1 embraces the stock at the reduced neck and cooperates with vtheplug to impart strength to the stock at the closedvend, so as to enableit to withstand the stresses that are incident to the stretchingoperation. The inner diameter of the stock is substantially equal to theouter diameter of the inner member I0, while the outer diameter of thestock is larger than the inner diameter of the member Il. Consequentlyit is necessary to reduce the wall thickness of the stock, and this I'accomplish by stretching it during the assembly operation. l

The method by which I insert the elastic bushing between the inner andouter members comprises the insertion of a long -continuous tube Illainto the stock until the forward end of it engages an annular shoulder20 at the inner end of the plug i6. The assembled unit is then placed ina machine and moved in an axial direction through a forming die 25,which partially reduces the diameter of the rubber sleeve from whence itis passed into the tube lla, which further reduces it to the finishedsize. The tube I Ia whenA removed from the machine becomes the outermember Il o`f the finished bushing. The machine, which I have shown forstretching the rubber during the inserting operation, may comprise anopen. frame which has sides 30, and ends 3| and 33v respectively.Between the ends there is a cross-member-2l, which supports the die 25and there are other cross members 22, and 23 each of which supports oneend of a tube Il a. In the illustration shown the end member 33functions likewise as a support for one of the tubes ila. While I haveillustrated the machine -as supporting three tubes Ila in tandemrelationship, it is to be understood that the machine is capableA of usewith any number of tubes and that it may be designed for tu of anylength.

To force the stock into thev outer member, I have shown an electricmotor` 35 which is adapted to rotate a gear 36 as by a belt drive 31.The gear 36 has the bore thereof threaded for engagement with a threadedspindle 38, which may be splined to a key 9 in one of the bearing caps39. The spindle may have one .end thereof connected to a carriage M thatis mounted for movement along the members. The connection is illustratedin detail in Fig. 10 wherein the end of the,spindle has a flange 80 thatfits loosely into an' opening 26 in a plate.` 21 that is fastened to thecarriage. The carriage is provided with a saddle 42 in which therearward end of the tube I0a is adapted to besupported,

the saddle. being U-shaped so that the tube together with the assembledstock thereon may It is to be vunderstood that the axis of the threadedspindle is coextensive with that of the tube and with thoseof the tubesIla.

To use the apparatus, the tube Ita is inserted into the rubber stockuntil it engages the closed end thereof whereupon the projecting end ofthe tube is placed within the'saddle I2. At such time the neck of thestock is disposed between the carriage Il and the die 25. The motor isthen started whereupon the operator guides the forward end of the stockinto the die. He then places one end of a tube lla into a U-shapedsaddle 45 o n the cross member 22 and manually guides the other end toreceive the moving unit that has passed through the die. The position ofthe parts at such time-is represented in. Fig. 2. As soon as the stockhas entered such tube,

`the operator is then free to place another tube in the saddle Ilia onthe cross-member 23 and guide' it in the same manner to receive theforwardly moving stock. The same operation is repeated until all of thetubes for which the machine has been designed have been assembled. It isunderstood that the length of the inner tube and of the rubber stock issuch that at the completion of the operation the reduced neck projectsbeyond the farmost end of the last outer tube. Thereupon, the unitarystructure which comprises the ,tube Illa, the vstretched rubber stockand the plurality of tubes I|a lifted from the machine and the motor isreversed to return the carriage to its initial position. The assembledunit which is shown in Fig. 11 is then cut into sections as along thelines a-a, each having a length of the outer tube'lla so that thefinished product corresponds to that shown in Fig. 4.l If desiredhowever the outer tube may comprise an elongated member from which,sections may becut transversely. In suchl case the tube supports 22 and23 would be eliminated andV the tube would be supported onvthe end 33.

A modification of-the rubber stock is shown in Fig. 5wherein the forwardend thereof is closed solely by the rubber wall which is reinforced by athickened portion 60 to resist the stresses that are imparted to itduring the stretching operation. To facilitate the uniform distributionof forces against the rubber,-I insert a plug 6I which is rounded toconform tothe shape yof the inner end wall ofthe stock, and which has anannular shoulder 62 for receiving the tube Illa'.

In making the stock either in the form shown inFig. 2l or in Fig. 5 therubber is cured on a 'mandreL which is removed before the tube ia isinserted therein. In addition, the outer surfaces of the tube issubjected to a grinding op eration, so that its Wall thicknessma-y beuni form throughout its length. l Moreover, to facilin tate the entranceof the stock into the die' and also into theouter tubes, I may applylubricant in the form of vaseline to the outer surface before the stockengages the diel 'Ihe reduction in size of the rubber stock through thediemay comprise `the only reduction employed, although if desired thestock may be reduced farther upon entering the outer tube. To facilitatethe reduction, the opening of the die -is tapered, as shown at 65 andthe wall of the vout evidence of fatigue.

An important advantage of the method dis- 1 closed herein is the factthat the bushing may be made in any length and then cut to the desiredsize, or if desired a large number of short bushings may be made at onetime. 'I'he method therefore possesses economical manufacturingfadvantages and assures uniform distribution of stresses in the stretchedrubber. The word freely as used in the claims means an elastic stockwhich is not bonded to the core.

I claimav 1. A method of making a resilient bushing which consists infreely supporting hollow elastic stock on a core, applying force to theleading end only of said stock to force the stock and core through areducing and stretching die whereby the stock is placed under tension,and forcingl the tensioned stock and core into a conning member of lessdiameter than the diameter of the tensioned. stock. v

2. A method of making a resilient bushing which consists in freelysupporting hollow elastic stock on a core, forcing the stock and corethrough a reducing and stretching die by applying force only to theleading end thereof to tension the same and to cause the stock to iowfrom the leading toward the trailing end thereof and equally distributethe stresses throughout the samel and then forcing the tensioned stockand core into a confining member of less diameter than the diameter ofthe tensioned stock.

3. A method of making a resilient bushing which consists in freelysupporting hollow, elastic stock on a core, forcing the stock and coreinto a reducing and stretching confining member having s, diameter lessthan the diameter of the tensioned stock by applying force to theleading end only of the stock. f

4. A method of making' resilient bushings which consists in freelysupporting hollow elastic stock on a core, forcing the stock and coresimultaneously into a reducing andl stretching confinving member havinga diameter less than the .tic stock upon a core, forcingv the stock andcore into a reducing, stretching and'conflning member having a diameterless than the diameter of the tensioned stock by applying force to theleading end only of the stock, and moving the stock and core at a ratethat will stretch the stock uniformly from end to end within theconfining member. l l

OSCAR B. WELKER.

